Answer: The missing coefficient is 2.
Explanation:
According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.

As in the products, there are 2 atoms of sodium, thus there will be 2 atoms of of sodium in the reactant as well. This will balance the number of hydrogen and oxygen atoms as well.
Thus the missing coefficient is 2.
Answer:
Eutrophication is the enrichment of a body of water with excessive nutrients (nitrogen and phosphorus), which causes algal growth and subsequent decline of dissolved oxygen after decomposition.
Answer:
3.384364 time 10^24 atoms
Explanation:
multiply by avogadro's number